Dual power polarity protector/indicator

FIELD OF THE INVENTION

The present invention relates in general to communication systems and components therefor, and is particularly directed a power supply interface circuit that is configured to prevent a circuit path of telecommunication equipment, such as a telephone line test device, containing an circuit interruption device (such as a fuse or circuit breaker), from being subjected to an improper (reverse) connection to a power source therefor (such as a primary power source and an auxiliary battery), so that the circuit interruption device will not be tripped thereby. In addition, the inventive interface circuit includes an indicator circuit that is operative to indicate whether the device's power terminals are properly connected to each power source, so that, if inadvertently reverse-connected, the wires can be properly reconnected, and thereby provide for delivery of power to the device from either power source, as required.

BACKGROUND OF THE INVENTION

Users of telecommunication system equipment often install one or more auxiliary devices, such as but not limited to test units and the like, at either or both of host (central office (CO)) and remote (customer premises) sites of the system. In addition to being interfaced with communication links of the system proper, these devices must be properly powered. In some instances, the power may be drawn from the same wires used to send voice and/or data over the telephone lines. This type of powering, which is sourced from a CO battery (−48 VDC and ground (GND)), is commonly referred to as ‘loop’ or ‘span’ powering, and permits the phone company to remotely power equipment that may be located up to several miles from the central office.

Within the telephone networks of the continental United States, loop powering is used extensively on mid-span devices (rather than termination devices) in DDS, ISDN, T<b>1</b>, HDSL, and other digital networks. Terminating devices for digital data services are generally not span-powered; instead, being typically located within the customer's premises, they receive power from the customer's local utility feed. In addition, the auxiliary device may not continuously require span-supplied power, or it may use this power only during emergency situations.

Where the auxiliary device is powered from a local utility, as in the case of equipment installed at the customer's premises, a loss of local power (for example during a lighting storm) will cause the terminating device to stop functioning. This is problematic for digital services (such as ISDN) that implement plain-old-telephone-service (POTS) support. Thus, a local power failure will cause a loss of phone service (including emergency service, such as the ability to place a 911 call). As a consequence, digital service customers have traditionally been required to maintain a separate standard analog phone line, in addition to the digital data line(s).

Irrespective of the need to provide auxiliary POTS service, the type of equipment employed, or whether the equipment is located within the central office or at a remote site, it has become common practice to employ multiple (dual) power feeds, one serving as a primary supply, and the other providing an auxiliary back-up. These two feeds typically include a CO battery, as well as an auxiliary DC supply, that are “OR”-fed to the auxiliary circuit of interest through a circuit interruption or protection device, such as a fuse or circuit breaker. Unfortunately, during installation of the equipment, it sometime happens that one or both pairs of power supply leads are miss-wired (reversed)—resulting in triggering the operation of the protection device (i.e., tripping the circuit breaker or blowing the fuse).

SUMMARY OF THE INVENTION

In accordance with the present invention, this problem is effectively obviated by a new and improved power supply interface circuit, that is configured to prevent the power supply path to the telecommunication circuitry, which contains a circuit interruption or protection device, from being subjected to an improper (reverse) connection of the device's power terminals to one or more power sources. In addition, the invention contains a polarity indicator circuit that is operative to indicate whether the device's power terminals are properly connected to a power source, so that if inadvertently reversed, the wires can be properly reconnected, and thereby provide for delivery of power from either power source, as required.

For this purpose, respective sets of power supply connection terminals are provided to allow connection to respectively different sources (e.g. a primary (CO) supply and a back-up supply) capable of providing operational power for the telecommunication circuit. Each set of terminals includes one terminal to be coupled to the relatively positive power supply voltage (e.g., ground) and a second terminal to be coupled to the relatively negative power supply voltage (−48 VDC).

Each set of power supply terminals is connected to respective nodes of the power supply circuit path through diodes, which are forward conducting for only a proper polarity connection of the power supply connection terminal to a respective power source, but prevent the protection device from being triggered in the event of an improper (reverse) connection of either set of power terminals to its associated power sources.

In addition, to indicate whether the power supply terminals are connected to the proper polarity supply voltage, a polarity indicator circuit, containing one or more light emitting diodes, is coupled across each set of power supply connection terminals.

BRIEF DESCRIPTION OF THE DRAWINGS

The single FIGURE is a schematically illustration of the multi-power supply interface circuit of the present invention.

DETAILED DESCRIPTION

Referring now to the single FIGURE, the multi-power supply interface circuit of the present invention is schematically shown as comprising multiple sets (pairs) of power supply connection terminals <b>10</b> and <b>20</b>, each of which is associated with a respective source of DC power that supplies operational power for a telecommunication circuit (or load) <b>30</b>, such as but not limited to a piece of telephone line test circuit. A circuit path <b>33</b> through which power is supplied to the telecommunication circuit <b>30</b> includes a circuit interruption or protection device, such as a fuse or circuit breaker <b>35</b>.

For purposes of providing a non-limiting embodiment, each DC power source provides a differential voltage pair customarily used in present day telecommunication networks, including a relatively positive voltage (ground (GND) and a relatively negative voltage (−48 VDC). Also, while the Figure shows only two sets of power supply connection terminals, it is to be observed that the invention may be used with a different number of power supply connection terminals without departing from the invention.

The first set of power supply terminals <b>10</b> includes a first terminal <b>11</b> that is intended to be coupled to the relatively positive power supply voltage (GND) and a second terminal <b>12</b> that is intended to be coupled to the relatively negative power supply voltage (−48 VDC). Likewise, the second set of power supply terminals <b>20</b> includes a first terminal <b>21</b> intended to be coupled to the relatively positive power supply voltage (GND) and a second terminal <b>22</b> intended to be coupled to the relatively negative power supply voltage (−48 VDC).

Pursuant to the invention, connections for each set of power supply terminals to nodes <b>31</b> and <b>32</b> of the power supply circuit path <b>33</b> include respective sets of unidirectional current flow devices (diodes) <b>41</b>, <b>42</b> and <b>51</b>, <b>52</b>, coupled in a manner that prevents the protection device <b>35</b> from being triggered in the event of an improper (reverse) connection of either set of power terminals to its associated power sources. In particular, each diode is connected between a respective power supply connection terminal and one of the circuit path's nodes, so that the diode is forward conducting for only a proper polarity connection of the power supply connection terminal to a respective power source.

Thus, in the illustrated example, for interfacing with the first set of power supply connection terminals <b>10</b>, diode <b>41</b> has its anode <b>41</b>A connected to the relatively positive (GND) power source terminal <b>11</b> and its cathode <b>41</b>K connected to node <b>31</b>, while diode <b>42</b> has its cathode <b>42</b>K connected to the relatively negative (−48 VDC) power source terminal <b>12</b> and its anode <b>42</b>A connected to node <b>32</b>. Similarly, for interfacing with the second set of power supply connection terminals <b>20</b>, diode <b>51</b> has its anode <b>51</b>A connected to the relatively positive (GND) power source terminal <b>21</b> and its cathode <b>51</b>K connected to node <b>31</b>, while diode <b>52</b> has its cathode <b>52</b>K connected to the relatively negative (−48 VDC) power source terminal <b>22</b> and its anode <b>52</b>A connected to node <b>32</b>.

In order to alert the user as to whether a respective set of power supply terminals is properly (correct polarity) connected to the supply voltage inputs, a respective polarity indicator circuit is coupled across each set of power supply connection terminals. Specifically, a first polarity indicator circuit <b>60</b>, shown as having a light emitting diode (such as a ‘green’ LED) <b>61</b> in series with a resistor <b>63</b> is coupled across power supply connection terminals <b>11</b> and <b>12</b>, while a second polarity indicator circuit <b>70</b>, shown as having a light emitting diode <b>71</b> in series with a resistor <b>73</b> is coupled across power supply connection terminals <b>21</b> and <b>22</b>. As an adjunct measure, each polarity indicator circuit may also be provided with a reverse polarity ‘red’ LED, respectively shown at <b>65</b> and <b>75</b>, to indicate improper power supply connectivity.

In operation, as long as a respective set of power supply connection terminals is properly connected to an associated power source, e.g., terminal <b>11</b> is coupled to a relatively positive power source polarity (e.g., GND) and terminal <b>12</b> is coupled to a relatively negative positive power source polarity (e.g., −48 VDC), each of its associated diodes (e.g., <b>41</b> and <b>42</b>) will be forward conducting, allowing load <b>30</b> to be supplied with operational power through the circuit path containing the protection device <b>35</b>. In addition, its associated polarity indicator (e.g., green LED <b>61</b>) will be forward biased, and thereby illuminated, to provide an indication that the power supply terminals are correctly wired. A like operation takes place for terminals <b>21</b> and <b>22</b> and associated diodes <b>51</b> and <b>42</b>, as well as their associated LED <b>71</b>. If a reverse polarity indicator is provided, that indicator will be reverse biased an not illuminated.

However, if either set of power supply connection terminals is improperly (reverse) connected to a power source, e.g., terminal <b>11</b> is coupled to a relatively negative power source polarity (e.g., −48 VDC) and terminal <b>12</b> is coupled to a positive power source polarity (e.g., GND), each of their associated diodes (e.g., diodes <b>41</b> and <b>42</b>) will be reverse-biased. This will block conduction therethrough, preventing a reverse polarity voltage from being coupled across the power supply circuit path to the load <b>30</b>, so that the protection device will not trip. In addition, its associated polarity indicator (e.g., ‘green’ LED <b>61</b>) will be reverse biased, so that it is not illuminated. Where a reverse wiring indicator (e.g. ‘red’ LED <b>65</b>) is provided, as described above, that LED will be forward biased as a result of the reverse battery connection, to alert the user that the power supply terminals are incorrectly wired.

As will be appreciated from the foregoing description, the power supply interface circuit of the invention both prevents the inadvertent miswiring of power supply leads to wrong polarity voltages of either primary or auxiliary DC supply voltages from triggering the operation of a circuit protection device, and also indicates whether the device's power terminals are properly connected to a power source, so that if inadvertently reversed, the wires can be properly reconnected, and thereby provide for delivery of power from either power source, as required.

While we have shown and described an embodiment in accordance with the present invention, it is to be understood that the same is not limited thereto but is susceptible to numerous changes and modifications as known to a person skilled in the art, and we therefore do not wish to be limited to the details shown and described herein, but intend to cover all such changes and modifications as are obvious to one of ordinary skill in the art.